This invention relates to a diazo-type material, which may be a one- or two-component material.
Diazo-type materials are subject to high loads by light during their use in reading apparatuses. For this reason, light stability of the image dyestuffs for a diazo material is an important criterion. At the same time, all other qualities of the system, such as thermal stability, light sensitivity, coupling kinetics and absorption behavior need to be optimally ensured.
A higher light stability of the dyestuffs may, for instance, be achieved through suitable substitution of the diazonium components and coupler. Here, however, the expenses involved with synthesis for manufacturing suitable components are very high, while efficiency, i.e. prevention of fading of the dyestuffs, is very low. Patent Nos. DE-PS 697 051, DE-PS 8 386 92 and DE-PS 8 649 51 describe azo dyestuffs as image dyestuffs for diazo-type materials which have been made light-fast through an altered molecular arrangement. It is easier to add substances to an established diazo system which prevent fading of the image dyestuffs in reading apparatuses or at least retard it.
Besides the improvement in light stability, other supplemental factors, such as system compatibility, reduced fogging tendency, ease of synthesis and short-waved absorption of the inhibitor, still need to be fulfilled.
The compounds and classes of compounds known in the prior art, such as sterically hindered phenols (DE-PS No. 1 772 981) and ethylene diamine compounds (DE-AS No. 1 797 322) as well as 3-anilino-pyrazole (DD-WP No. G 03 C/221 629), considering the relatively high expenses that have to be incurred with their synthesization, do not result in a correspondingly high improvement in light-fastness of the azo dyes. A favorable effect against the fading rate of dyestuffs has been achieved with phosphoric-acid-ester-anilides (DD-WP No. G 03 C/222 062) which are relatively easy to prepare. The range of their absorption maximum, however, lies to far in the diazonium salt band. This makes the duplication process harder.
The object of this invention is to improve light stability in diazo-type materials under the conditions present in reading apparatuses.
The light-protective substances known and used up to now have either low efficiency or do not, or only inadequately fulfill certain supplemental requirements, for instance suitability for defect-free duplication.